Table roll with means for removing longitudinal curvature



United States Patent 3,094,771 TABLE ROLL WITH MEANS FOR REMOVING LONGITUDINAL (IURVATURE John D. Robertson, Taunton, Mass, assignor to Mount Hope Machinery Company, Taunton, Mass, a corporation of Massachusetts Fiied June 13, 1961, Ser. No. 120,125 5 Claims. (Cl. 29116) This invention relates in general to web-supporting rolls, and more particularly comprises a new and improved roll having means for removing longitudinal curvature induced by its own weight together with the weight of and/or tension in a web or other material thereon. The invention finds particular utility in rolls of great length, such as are employed in forming the Wider webs of paper in Fourdrinier machines, but its use is not limited to rolls of particular lengths.

This application is a continuation-in-part of my copending application Serial No. 44,455, now abandoned, entitled Roll of Adjustable Longitudinal Axis, filed July 21, 1960.

In the manufacture of paper, as by a Fourdrinier paper machine, a thin suspension of fiber in water is deposited on a broad moving belt of fine brass wire screen. The belt, or wire as it is more popularly known, advances at speeds of 600 feet a minute or more toward a suction box which forces water out of the mat of fibers by atmospheric pressure. During the first stages of travel on the wire, a large percentage of the water content of the pulp seeps down through the wire, leaving a film of rather damp fibers on the wire surface.

The broad and relatively heavy wire is supported for longitudinal movement by a series of transverse table rolls which must be rigid to support their own weight plus the weight of the wire and the paper without sagging, and are therefore conventionally given a large diameter (16 inches, for example). In practice, several problems are created by the use of supporting rolls of large diameter. It has been found that the water draining through the wire tends to .collect in a pocket between the wire and the rolls. This pocket of water normally builds up along the upper quadrant of the discharge side of the roll and extends generally the entire length thereof. The collected water creates a rather high vacuum (up to 26 inches) which pulls the wire down and to a certain extent partly around the roll, deflecting it from the plane of its path of travel, thereby forming a transverse dip in the wire. During normal operations the vacuum repeatedly builds up and bursts. Whenever the vacuum breaks the wire snaps up and away from the roll, causing the fibrous pulp in that region to fly off the wire and spatter the surrounding partly-formed sheet.

While it has been appreciated that this problem can be substantially eliminated by using rolls of relatively small diameter to support the wire, there has heretofore been no roll of any great length available that would not sag under its own Weight and that of the wire. Since many machines now make a continuous sheet of paper 200 inches wide, it will be understood that the wire would be in the neighborhood of 17 feet in width and the supporting table rolls somewhat greater in length. If the table rolls sagged to any extent, the wire would assume a certain transverse concavity and the watery pulp would tend to run towards the center line instead of remaining evenly distributed over the wire. This would result in the production of paper of non-uniform thickness.

Because of the high speed of rotation involved, as well as the great length of the rolls, they must be dynamically well-balanced and relatively rigid to minimize radial vibration. This problem becomes greatly magni- 3,094,771 Patented June 25, 1963 fie d as the rolls are reduced in diameter, because the mo ment of inertia of the roll about axes normal to its longitudinal axis diminishes, and consequently the rigidity of the roll is reduced.

It is an object of the present invention to overcome the problems mentioned above by providing an improved table roll, which may be of relatively great length and relatively small diameter, with adjustable means for removing transverse deflection induced in the roll by its own weight or that of a load which it is designed to carry.

Another object of this invention is to provide means for removing longitudinal curvature from a roll intended to be straight.

Another object of this invention is to provide an improved roll having means for removing longitudinal curvature therefrom which roll at the same time retains maximum rigidity for a given weight and diameter.

Briefly stated, a preferred embodiment of this invention includes a stationary support and an outer sleeve received about a plurality of axially-spaced annular spools, which are rotatably mounted upon the support, the sleeve extending along the major portion of the length of the support. The support is of longitudinally uniform cross-section, and preferably comprises a hollow cylinder of substantially uniform wall thickness without longitudinal discontinuities. This configuration affords a maximum of rigidity against transverse deflection, for a given diameter and weight of support. The mass of the support is of critical importance, especially in view of the fact that the roll is commonly operated above its critical rotational speed; the mass of the support limits the amplitude of vibration of the roll at these speeds.

Transverse deflection or sag of a roll is induced by its own weight and that of loads supported thereon. Furthermore, available manufacturing methods produce some longitudinal curvature or runout in the support. For the elimination of longitudinal curvature according to the invention, a tension rod extends lengthwise through the support, parallel to but spaced vertically beneath an axis of the support. The ends of the tension rod are threaded and pass eccentrically through abutments secured in opposite ends of the support. Nuts engaging the rod ends may be tightened to apply an adjustable tension to the rod. Suflicient tension is applied to the rod to compress the support eccentrically endwise and thus bring the roll into axially straight alignment when the desired load is applied. When the load is removed, the roll may be curved with a slight upward convexity under the applied tension, but will be axially straight in actual use.

The combination in the improved roll of the eccentrioally located tension rod with the longitudinally-uni form support affords maximum rigidity in a roll of relatively small diameter, and yet affords eflective means for removing longitudinal curvature to maintain the roll axially straight.

Longitudinal curvature or runout of the unloaded support, arising from imperfect manufacturing methods, may also be largely eliminated by the use of the invention. This may be accomplished by locating the plane in which this curvature principally occurs, which is determined by points lying along the axis of the support; and by orienting the roll with this plane extending vertically, with the curvature of the roll axis turned to an upwardly concave position. Thus, the principal curvature of the axis of the roll, whether caused by manufacturing error or by load, lies in a vertical plane beneath the desired rectilinear axis of the roll, and may be substantially corrected by the improved means previously described.

Further objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment of the invention, referring to the accompanying drawings, in which:

FIG. 1 is a longitudinal elevation in section of a roll made according to this invention, adjusted to eliminate transverse deflection under a load;

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1, looking in the direction of the arrows; and

FIG. 3 is a view similar to FIG. 1, illustrating on an exaggerated scale the upwardly convex curvature of the adjusted roll which occurs after adjustment and upon removal of the designed load.

In FIGS. 1-3, a roll according to the invention is indicated generally at 10, and is shown in an adjusted axially straight condition in FIG. 1. The roll comprises a tubular support 12 of a hollow cylindrical cross-section which is longitudinally uniform and free of discontinuities. The support carries a series of spool assemblies 14 mounted in end-to-end relation. Each spool assembly 14 is rotatably mounted on a ball bearing unit '16, comprising an inner race 15 and an outer race 17 supporting an annular spool 18. A plurality of annular spacers 20 are mounted in alternating relation with the bearing races 15 along the support to evenly space the bearings, and to maintain sufiicient clearance between adjacent spools 18 to accommodate a slight curvature of the roll. A pair of locking rings 22 are provided at opposite ends of the assembly of spools and bearings for firmly securing them along the tubular support 12 by means of screws 23. A surface sleeve 24, which is preferably of a corrosion-resistant, hard, and moderately resilient material such as fiberglass or hard rubber, is engaged circumferentially about all of the spools 18, connecting them for rotation in unison with the sleeve about the support 12. A pair of annular caps 26 are fastened to the outermost ones of the spools 18 by any suit-able means (not shown); if desired, means may be provided to form a water-tight or lint-tight rotating seal with the support to protect the enclosed ball bearing units.

The end portions of the support 12 extend through and are supported by spherical bearing elements 28 which are mounted for relative canting movement of the support within bearing members 30' on fixed supports 32. When the center of the roll is deflected upwardly in an unloaded condition, as shown on an exaggerated scale in FIG. 3, the end portions cant downwardly slightly with respect to the longitudinal axis of the roll. However, the deflection is very slight, and is removed by adjustable means of the invention during actual use of the roll, under a load; plain cylindrical supports may therefore be substituted if desired.

Extending lengthwise through the support 12 is a tension rod 34- having threaded end portions 36. Stout abutrnents or end plates 37 are received in opposite ends of the support, and are provided with aligned openings to receive the end portions of the rod 34. It will be noted that these openings are formed eccentrically in the abutments so that the rod will be arranged parallel to, but spaced vertically beneath, the longitudinal axis of the roll. A pair of washers 38 and nuts 40' engage the ends of the rod and are tensioned against the abutments. By tightening the nuts 40, the rod 34 may be subjected to increasing tension, and the support may be placed under an eccentric longitudinal compressive force. This force is used to remove longitudinal curvature from the roll.

Assuming now that the roll of FIG. 1 is serving as a table roll in a Fourdrinier paper machine, a wire 42 supported by the roll carries a watery film of paper fiber 44. In view of the fact that the wire may exceed 17 feet in width, the table roll would have to be about 20 feet in length. The roll can be supported only as its end portions, and to prevent it from sagging to any appreciable extent, rolls heretofore have been provided with large outside diameters in the neighborhood of 16 inches. As

pointed out above, table rolls of such large diameter have a disturbing effect in the formation of paper by reason of the high suction created between the roll and the wire.

Now, however, according to the present invention a table roll of suitable length may be made of smaller diameter (10 inches, for example), and can be adjusted to eliminate longitudinal curvatures induced by its own weight, by a supported load, or by imperfect manufacture. In practice, the roll is mounted horizontally with the rod located along the bottom of the support, and before adjustment will display a definite amount of downward deflection or sag.

The support is preferably first inspected to determine the principal plane of curvature of the longitudinal axis resulting from runout in its manufacture, and is mounted with this plane vertical, and with the curve of the axis upwardly concave. The load which the roll is to carry in normal operation is placed thereon, and the nuts 40 are tightened until the rod is sufficiently tensioned to bring the roll into an axially straight condition. Should the load be increased or decreased for any reason, the tension may be adjusted accordingly by tightening up or backing off the nuts 40, as necessary. It will be apparent that if the normal load is removed for any reason after the adjustment has been made, the roll will assume a slight upward deflection, as is illustrated on an exaggerated scale in FIG. 3.

Several distinct advantages are immediately realizable from the improved rolls. Table rolls of great length may now be made with a greatly reduced diameter, without sacrificing longitudinal straightness. By employing table rolls of small diameter in a paper machine, there is considerably less contact with the wire and a corresponding reduction in suction so that the disturbance previously encountered by the use of large diameter rolls is substantially eliminated. By using a greater number of small diameter rolls mounted relatively close together, the wire is better supported than by a few large rolls. The increased number of small diameter rolls provides smoother drainage across the wire, due to the additional number of lines of contact between the wire and the rolls, and to the fact that the rolls may be grouped more closely together.

In the improved roll, as contrasted with conventional table rolls, a relatively small portion of the total mass rotates, so that the forces induced by dynamic imbalance are reduced, and there is correspondingly less vibration or whip. Furthermore, since operation of the improved roll will commonly be above the critical speed, the stationary mass of the tubular support will tend to restrain the rotating sleeve and spools from vibrating.

The improved construction also permits a reduction in the number of bearings in each roll. Since a conventional roll will sag to a certain extent, a relatively large number of ball bearing units must be used at relatively close intervals to accommodate the longitudinal curvature of the roll. These ball bearing units are quite expensive and constitute a considerable portion of the total cost of the roll. In view of the fact that the present roll can be maintained axially straight in a heavily loaded condition, the number of ball bearing units needed to support the sleeve can be substantially reduced, thereby effecting a marked saving in the total cost of the roll.

The roll described herein may be advantageously utilized in a variety of applications, such as conveyor systems or other installations Where there is a need for maintaining a roll axis straight, and a rigid roll structure is required.

It is to be understood that the foregoing description of a preferred embodiment of the invention is given for purposes of illustration, and that various changes and modifications may be made Without departing from the true spirit and scope of the invention.

Having thus disclosed the invention, what I claim and desire to secure by Letters Patent of the United States is:

1. A roll comprising anelongated tubular support of longitudinally uniform and substantially symmetrical cross-section, a sleeve, means supporting said sleeve against transverse sagging and mounting said sleeve for rotation about said support at at least three axially spaced points, and means for adjustably compressing said support longitudinally and eccentrically to eliminate longitudinal curvature of said roll.

2. A roll comprising a tubular support of longitudinally uniform and substantially symmetrical cross-section, a sleeve, means supporting said sleeve against transverse sagging and mounting said sleeve for rotation on said support at at least three axially spaced points, a rod extending longitudinally and eccentrically interiorly through said support, the end portions of said support being provided with means for tensioning said rod and applying the compressional reaction to said support to eliminate longitudinal curvature of said roll.

3. A roll comprising a tubular support having a longitudinally uniform and substantially symmetrical crosssection, means mounting said support horizontally, an annular sleeve, means supporting said sleeve against transverse sagging and mounting said sleeve upon said support at at least three axially spaced points for rotation about a rectilinear axis, said support being subject to external forces which produce longitudinal bowing in a plane of curvature, a rod extending longitudinally and interiorly through said support eccentrically of said axis, said rod lying along said plane of curvature, and the curvature of said roll in said plane lying concave away from said rod, the end portions of said support being provided with means for tensioning said rod and applying the compressional reaction eccentrically to said support to eliminate said longitudinal bowing of said roll.

4. A roll comprising an elongated tubular support of longitudinally uniform and substantially symmetrical cross-section, means mounting said support horizontally, a pair of abutments engaging the opposite ends of said support, an annular sleeve, means supporting said sleeve against transverse sagging and mounting said sleeve upon said support, at at least three axially spaced points for rotation about a rectilinear axis, said support being subject to externally applied forces which produce longitudinal bowing in a plane of curvature, a rod extending longitudinally and interiorly through said support and said abutments eccentrically of said axis, said rod lying along said plane of curvature, and the curvature of said roll in said plane lying concave away from said rod, and means engaging the end portions of said rod protruding from said abutments for tensioning said rod and applying the compressional reaction through said abutments eccentrically to said support to eliminate said longitudinal bowing of said roll.

5. A roll comprising an elongated tubular support of longitudinally uniform and substantially symmetrical cross-section, means mounting said support horizontally, a pair of abutments engaging the opposite ends of said support, an annular sleeve, means supporting said sleeve against transverse sagging and mounting said sleeve upon said support, at at least three axially spaced points for rotation about a rectilinear axis, said support being subject to externally applied forces which produce longitudinal bowing in a plane of curvature, a rod extending longitudinally and interiorly through said support and said abutments eccentrically of said axis, said rod lying along said plane of curvature, and the curvature of said roll in said plane lying concave away from said rod, and nuts threadedly engaged on the ends of said rod protruding from said abutments =for adjustably tensioning said rod and applying the compressional reaction through said abutments to said support eccentrically of said axis to eliminate said longitudinal curvature of said roll.

References Cited in the file of this patent UNITED STATES PATENTS 2,952,889 Hanssen Sept. 24, 1960 

1. A ROLL COMPRISING AN ELONGATED TUBULAR SUPPORT OF LONGITUDINALLY UNIFORM AND SUBSTANTIALLY SYMMETRICAL CROSS-SECTION, A SLEEVE, MEANS SUPPORTING SAID SLEEVE AGAINST TRANSVERSE SAGGING AND MOUNTING SAID SLEEVE FOR ROTATION ABOUT SAID SUPPORT AT AT LEAST THREE AXIALLY SPACED POINTS, AND MEANS FOR ADJUSTABLY COMPRESSING SAID SUPPORT LONGITUDINALLY AND ECCENTRICALLY TO ELIMINATE LONGITUDINAL CURVATURE OF SAID ROLL. 